Sensitive latching relay



Oct. 25, 1966 I W- M. GRENGG SENSITIVE LATCHING RELAY 2 Sheets-Sheet 1 Filed Sept. 16, 1965 J. (Sm/way) JZ 3. (Wm/2 7E0) r? a Mfl w fir. g f w Oct. 25, 1966 W. M. GRENGG 3,281,739

SENSITIVE LATCHING RELAY Filed Sept. 16, 1963 2 Sheets-Sheet 2 IV S United States Patent O SENSITIVE LATCHING RELAY Walter M. Grengg, Madison, Wis., assignor to Phillips- Eckardt Electronic Corporation, Joliet, 11]., a corporation of Illinois Filed Sept. 16, 1963, Ser. No. 309,263 11 Claims. (Cl. 335-229) This invention relates to a single shot relay whose operation is triggered from a standby state by a very small and momentary input of electrical energy, the relay being thereby extremely sensitive.

One object of the invention is to provide a relay which once operated remains in the operated state until it is reset.

Another object is to provide a latching type relay which utilizes a permanent magnet to maintain the relay in the operated state and which is also effective to maintain it in the standby state when the parts thereof are initially positioned in that state.

Still another object is to provide a relay which can be operated by a very small input of electrical energy for a very short duration of time.

A further object is to provide a relay which is latched in the standby state by a novel pointed pole structure which serves to concentrate magnet flux at the latching point, the magnetic flux being produced by a perma-' nent magnet.

Still a further object is to provide a relay in which there are no springs so that high resistance to vibration failure can be achieved.

An additional object is to provide a relay normally latched in standby state, which after being operated by the passage of a small surge of current through the coil thereof for testing purposes, may then be reset by passage of a larger current through its coil which again positions the armature in the standby position.

Another additional object is to provide a latching type relay suitable for actuating switches, valves, clutches or other devices requiring power such as capable of delivery by my relay in response to a minute operating surge of electrical energy.

With these and other objects in view, my invention consists in the construction, arrangement and combination of the various parts of my sensitive latching relay, whereby the objects above contemplated are attained, as hereinafter more fully set forth, pointed out in my claims and illustrated in detail on the accompanying drawing, wherein:

FIG. 1 is a diagrammatic view of the components of my relay showing the same in STANDBY state and the resulting magnetic flux pattern;

FIG. 2 is a similar diagrammatic view showing the relay in OPERATE state;

FIGS. 3 and 4 are similar diagrammatic views showing the relay in OPERATED and RESET states respectively;

FIG. 5 is a diagrammatic view somewhat similar to FIG. 1 but including terms involved in the calculations for the design of my relay;

FIG. 6 is a sectional view on the line 5-5 of FIG. 1 to show one way of mounting the armature and contacts of a controlled circuit operated thereby, and

FIGS. 7 to 11 are diagrammatic views showing modifications of the permanent magnet, core and armature arrangement possible with a relay of the type herein disclosed.

On the accompanying drawings, and first referring to FIGS. 1 to 5, I have used the reference numeral 12 to indicate a soft ferromagnetic frame having a core portion 14 on which is mounted a coil 15. The end of the core portion 14 is pointed as indicated at 16 which results in a relatively small terminal end 18 constituting an armature-contacting portion against which an armature 20 is positioned in the standby state of the relay as shown in FIG. 1. A permanent magnet 22 is interposed in the ferromagnetic path adjacent the armature 20 and has a stop 24 thereon of non-magnetic material.

The armature 20 is adapted to assume either the position of FIG. 1 or the position of FIG. 3, and may be pivoted as at 26 as shown at FIG. 6 to permit the movement of the armature from one position to the other. The armature may actuate any desired control device such as switch contacts 28 and 30. Thus the relay utilizes a small current in the coil 15 to control larger currents through the switch contacts 28 and 30. A balanced armature is preferred to minimize the effects of shock and vibration.

The invention disclosed has to do with a sensitive latching relay which can be tested and reset an indefinite number of times. High contact pressure and vibration resistance (partially accomplished by the elimination of all springs) is an important feature of the invention in addition to extreme sensitivity.

Assuming the parts are in the standby state illustrated in FIG. 1, arrows are used to illustrate two paths of magnetic flux flow. Such flow is induced by the permanent magnet 22 and passes through the spacer 24 and into the armature 20 in the directions shown by the arrowheads. In addition to the flux flow path shown by medium weight arrows, there is a flux flow path indicated by light weight arrows and a flux concentration at the terminal end 18 of the pointed pole 16 due to the small area involved which provides the holding force for the armature in the upper position. This force is greater due to such flux concentration than the force of the permanent magnet 22 pulling the armature down. An important design consideration for proper latching in the standby state is that the relation between the magnetic flux in the core (b (see FIG, 5), the effective contact area A at the pointed pole, the flux in the air gap (p and the effective cross sectional area of the air gap A is as follows:

for latching and 48. This effectively reduce so that the required inequality for latching no longer is maintained.

The weakening of the flux in the core 12 and in the armature 20 is indicated in FIG. 2 by dotted arrows. The flux direction at the moment of the release is in the same direction as FIG. 1 but the counter magnetomotive force produced by the coil 15 has changed the relative flux densities. This reduces the pull of the terminal end 18 on the armature 20 whereupon the permanent magnet pulls the armature down to the operated position shown in FIG. 3. Thereupon a new flux pattern is established as illustrated. The armature is now being held down by the permanent magnet with considerable force instead of being held up with considerable force as in FIG. 1. The area A should be less than half the area A for effective operation.

In order to reset the relay, a heavier current may be supplied to the coil 15, preferably in the reverse direction as indicated by the arrow 50 in FIG. 4 and a new flux pattern is established indicated by heavy weight arrows, the magnetic pull as between the terminal end 18 and the armature 20 now being greater than the pull of the magnet 22 through the spacer 24 on the armature. The armature thereupon moves up to the standby state shown in FIG. 1 and remains latched in this position until triggered again as illustrated in FIG. 2. I

The reset current may flow in either direction. FIG. 4 indicates the preferred direction. The armature can be reset at about the same expenditure of reset power with the heavy current flowing in the opposite direction but there is then a moment of instability as the flux directions rearrange themselves relative to the pattern of FIG. 1 after the reset current stops. Vibration during this instant of instability could inadvertently release the armature.

As to the amount of electrical power required for operation of my relay, by way of example if the relay is of miniature dimensions such as a volume of /2 cubic inch, about 2 milliwatts is sufficient when the coil 15 is energized as in FIG. 2, and only a few milliseconds duration is required. On the other hand, the reset power required may be as much as 400 or 500 milliwatts for a few milliseconds. The standby flux pattern and. the operated flux pattern are such that the armature is held in either of its extreme positions with considerable force but can be released from the standby position by a small surge of current. While I have shown the permanent magnet 22 of indicated polarity, the polarity may be reversed and the operating currents likewise reversed and the relay would operate equally well. The motion produced in the armatures of the structures above described can bviously be used. for many purposes other than the closure of switch contacts.

The basic frame, core, armature and permanent magnet arrangement thus far described forms a ferromagnetic path which has three air gaps G1, G2 and G3- asshown in FIG. 5, G1 being the gap between the top of the armature 20 and the lower end 18 of the pointed portion 16 of the core 14 when the armature is down as shown for instance in FIG. 3. This basic structure may be modified in shape and arrangement such as shown in FIG. 7. Parts comparable to FIGS. 1 to bear the same reference numerals with the addition of a.

FIG. 8 shows another modification in which a permanent magnet 22b is differently arrangedv and the armature 20b is held. thereto by magnetic attraction, a curved surface 26b of the magnet being provided for a curved seat of the armature to rock on for pivoting action.

FIG. 9 shows still another arrangement wherein the relatively small terminal end 180 is on the armature 200 instead of on the core. This arrangement works equally as well as the reverse shown in FIGS. 6, 7 and 8, or relatively small terminal ends may be provided on both the core and the armature. The ferromagnetic system in the relay of FIG. 9 includes a projecting portion 29 adjacent the pivot of the armature anda projecting portion 31 adjacent the end of the armature remote from the terminal end 18c. The portion 31 acts as an extension of one pole of the magnet 22c. Also instead of the stop 240 being mounted. on the magnet as in FIGS 6, 7, and 8, it may be mounted independent thereof as shown in FIG. 9, another design variation possible in a relay of this type.

FIG. is comparable to FIG. 7 with the magnet 22d positioned differently, and an extension 32 comparable to the extension 31 of FIG. 9 bridging the interval between the magnet and the spacer 24d.

In FIG. 11 the ferromagnetic frame 12e has a U-shaped portion 33 providing air gaps at opposite sides of the armature 20c comparable to those labeled G3 in FIG. 5, the permanent magnet 22c being located between the arms of the U-shaped portion 33 and at the end of the armature 20a opposite the end that contacts the ferromagnetic frame end 18e of reduced cross section.

Some changes may be made in the construction and arrangement of the parts of my sensitive latching relay without departing from the real spirit and purpose of my invention, and it is my intention to cover by my claims any modified forms of structure or use of mechanical equivalents which may reasonably be included within their scope.

I claim as my invention:

1. In a sensitive latching relay of the character described, an armature, a ferromagnetic frame having a terminal end adjacent a first portion of said armature and constituting a first air. gap between said armature and said ferromagnetic frame, a permanent magnet between said ferromagnetic frame and an opposite portion of said armature, said opposite portion of said armature and the end of said permanent magnet thereadjacent constituting a second air gap to provide a flux flow path including said first air gap, said armature and said second air gap, said first air gap having a cross sectional area between the surfaces of nearest approach which is less than half of the cross sectional area of the said second air gap to concentrate magnetic fiux through said first air gap to retain said armature in contact with said terminal end in opposition to the pull of said permanent magnet through said second air gap, a coil on said ferromagnetic frame to reduce magnetic flux flow through said ferromagnetic frame and said armature upon flow of current through said. coil whereby said armature will be attracted by said permanent magnet away from said terminal end, and said ferromagnetic frame having another portion adjacent a third portion of said armature, said last two mentioned portions constituting a third air gap to provide a magnetic flux flow path from said armature through said coil to said terminal end and. a flux flow path from said armature through said ferromagnetic frame to the end of said permanent magnet adjacent thereto.

2. A relay as claimed in claim 1 requiring only a small current of short duration in said coil to effect reduction of magnetic flux to permit said armature to be attracted toward said permanent magnet.

3. A relay as claimed in claim 2 wherein a heavy current in said coil effects movement of said armature away from said permanent magnet and into contact with said terminal end.

4. A relay as claimed in claim 1 having means to stop said armature spaced from said permanent magnet.

5. A relay as claimed in claim 1 wherein said ferromagnetic frame has an additional portion thereof interposed between said permanent magnet and said armature.

6. A relay as claimed in claim 5 having means to stop said armature spaced from said additional portion of said ferromagnetic frame.

7. A relay in accordance with claim 4 wherein said means for stopping said armature comprises a spacer between said magnet and said armature.

8. In a relay, a ferromagnetic frame and a permanent magnet contiguous to each other and having an air gap between a terminal end of said frame and one pole of said permanent magnet, an armature having a portion movable in said air gap between one position of contact with said terminal end and spaced from said magnet, and another position adjacent said magnet and out of contact with said terminal end, stop means for said armature in the latter position, said portion of said armature being reduced in cross section to concentrate magnetic flux from said armature to said terminal end to retain said armature in contact therewith in opposition to the pull of said permanent magnet, and an electrically energizable coil means, on said. ferromagnetic frame, operable when energized, to reduce the magnetic flux flow across said terminal end and said armature whereupon said armature is attracted toward said permanent magnet.

9. In a sensitive relay, a means providing a ferromagnetic path, a permanent magnet having one pole adjacent one end of said means, said means and said permanent magnet being arranged to provide an air gap between the other pole of said permanent magnet and the other end of said means, an armature movable in said air gap to a standby position position substantially in contact with said other end of said means and an operated position adjacent said other pole of said magnet, said other end of said means being reduced in cross section to cause magnetic flux concentration when said armature is in said standby position, thereby to retain said armature thereagainst in opposition to the pull of said magnet on said armature, and an electro-magnetic coil on said means for momentarily weakening the flux flow through said reduced cross section, thereby to permit said armature to be attracted by said permanent magnet to operated. position.

10. A latching relay comprising means forming a ferromagnetic path, a permanent magnet having one pole adjacent one end of said means, said means and said permanent magnet being arranged to provide a primary air gap between the other pole of said permanent magnet and the other end of said means, an armature having one portion movable in said primary air gap to either a standby position substantially in contact with said other end of said means and an operated position adjacent said other pole of said magnet, said other end of said means being reduced in cross section to cause magnetic flux concentration when said armature is substantially in contact with said other end of said means thereby to retain said armature in opposition to the pull of said permanent magnet on said armature, said armature having another portion thereof closely adjacent a portion of said. means for flux flow through a secondary air gap between the two, and an electrically energized coil on said means for momentarily weakening the flux flow through said reduced cross section thereby to permit said armature to be attracted by said permanent magnet to operated position.

11. A latching relay comprising means forming a ferromagnetic path, a permanent magnet having one pole adjacent one end of said means, an armature movable to a standby position substantially in contact with said other end. of said means and an operated position adjacent said pole of said magnet, said other end of said means being reduced in cross section to cause magnetic flux concentration when said armature is in said standby position thereby to retain said armature in opposition to the pull of said permanent magnet pole on said armature, said armature having the central portion thereof substantially in pivoted contact with the other pole of said permanent magnet, and electrically energized means for momentarily weakening the flux flow through said reduced cross section thereby to permit said armature to be attracted by said permanent magnet to the operated position.

References Cited by the Examiner UNITED STATES PATENTS 2,818,478 12/1957 Bullen et a1. 317l7 2 X 2,882,459 4/1959 Berglund 317-171 X FOREIGN PATENTS 162,290 2/ 1958 Sweden.

BERNARD A. GILHEANY, Primary Examiner.

JOHN F. BURNS, ROBERT K. SCHAEFER, Examiners.

G. HARRIS, JR., Assistant Examiner. 

1. IN A SENSITIVE LATCHING RELAY OF THE CHARACTER DESCRIBED,. AN ARMATURE, A FERROMAGNETIC FRAME HAVING A TERMINAL END ADJACENT A FIRST PORTION OF SAID ARMATURE AND CONSTITUTING A FIRST AIR GAP BETWEEN SAID ARMATURE AND SAID FERROMAGNETIC FRAME, A PERMANENT MAGNET BETWEEN SAID FERROMAGNETIC FRAME, AND AN OPPOSITE PORTION OF SAID ARMATURE, SAID OPPOSITE PORTION OF SAID ARMATURE AND THE END OF SAID PERMANENT MAGNET THEREADJACENT CONSTITUTING A SECOND AIR GAP TO PROVIDE A FLUX FLOW PATH INCLUDING SAID FIRST AIR GAP, SAID ARMATURE AND SAID SECOND AIR GAP, SAID FIRST AIR GAP HAVING A CROSS SECTIONAL AREA BETWEEN THE SURFACES OF NEAREST APPROACH WHICH IS LESS THAN HALF OF THE CROSS SECTIONAL AREA OF THE SAID SECOND AIR GAP TO CONCENTRATE MAGNETIC FLUX THROUGH SAID FIRST AIR GAP TO RETAIN SAID ARMATURE IN CONTACT WITH SAID TERMINAL END IN OPPOSITION TO THE PULL OF SAID PERMANENT MAGNET THROUGH SAID SECOND AIR GAP, A COIL ON SAID FERROMAGNETIC FRAME TO REDUCE MAGNETIC FLUX FLOW THROUGH SAID FERROMAGNETIC FRAME AND SAID ARMATURE UPON FLOW OF CURRENT THROUGH SAID COIL WHEREBY SAID ARMATURE WILL BE ATTRACTED BY SAID PERMANENT MAGNET AWAY FROM SAID TERMINAL END, ANS SAID FERROMAGNETIC FROM HAVING ANOTHER PORTION ADJACENT A THIRD PORTION OF SAID ARMATURE, SAID LAST TWO MENTIONED PORTIONS CONSTITUTING A THIRD AIR GAP TO PROVIDE A MAGNETIC FLUX FLOW PATH FROM SAID ARMATURE THROUGH SAID COIL TO SAID TERMINAL END AND A FLUX FLOW PATH FROM SAID ARMATURE THROUGH SAID FERROMAGNETIC FRAME TO THE END OF SAID PERMANENT MAGNET ADJACENT THERETO. 